Sound-wave translating device



` following Patented oci. 13, 192s.

issuer UNITED stares Parser orifice.

Josera sLnrIAN,

OF SWISSVALE, PENNSYLVANIA, ASSIGNOB. T0 WESTINGHOUSB ELECTRIC 'MANUF AS;J'LTIILIITG COMPANY, AQOBPORAIION 0F PEINNSYIZ'VANIA.v

'SOUND-WAVE mannerisms Dmcn Application led October 28, 1922. Serial Ho. 567,568.

To all whom, 'it-may concern:

Be it known that 1,JossrHSiinmAn, u citizen of the United States, and a resident of Swissvale, in the countyfof Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Sound iVm-'e Translating Devices, of which the is a specification.

My invention relates to telephone systems and apparatus, having particular'relation to an improved soundwave translating device; V

One object of my invention is `to provide a translating device of 'the class described wherein sound waves muy be faithfully translated into correspondingly modulated electrical energy without impairing the quality, tone and quantity of the translated energy and without introducing distorting harmonics.

Another object ofmy invention is to provide a telephone translating apparatus which embodies no moving parts and more especially one wherein the usual vibratory diaphragm is eliminated.

A further object of my invention is to. provide a soundwave translating device which is characterized by its simplicity of design, elliciency of operation and lack or" complicated adjustments and which lends itself to inexpensive methods of manufacture, the several parts of which .may be easily made by existing automatic machinerj,Y and may readily be assembled with a minimum expenditure of time and money.

The ordinary resistor microphone .ofthe carbon-capsule type has certain inherent un desirable .characteristics well known to those .skilled in 'the art, as, for instance, a vibratory element which not only tends to introduce distortion but also complicates the structure of the-transmitter, and requires adjustment.

According to my invention, I provide nn improved sound-wave transl-ating system 'for accomplishing the' desired results just mentioned and others hereinafter set vforth in Fill the following description. The translating syste-In embodying my invention is based upon experiments showing lthat a very fino chain of granules, is extremely sensitive to pressure variations incident, for instance, to. the presence of sound waves. The chain of granules may be formedora number .of ditferent materials, as for instance, metallic ce' militeria or carbon, preferably' the latter..

.in one embodi lent of my invention, a chain is formed between a sur of spaced electrodes, which are energize from a source of energy through a constant-current high-- impedance resistance device, either by bringing; said electrodes in Contact and then separating the same or by establishing electrostatic forces in the space between the 4electrodes. The potentiel variations across the ends of the chain correspond 'to vvariations in the resistance thereof and maybe amplified by a three-electrode repeater device of any well known type.

With these and other objects in view, i

my invention further consists in the nature, the details of construction and the metliod of operation hereinafter described and claimed and illustrated in the accompanying,

drawing, wherein the single 'figure is a diagrammatic view of circuits' and apparatus embodying my invention.

In the illustrated embodiment of my invention shown in the drawing, a pair of spaced relatively movable electrodes l and 2 m" a translating device 3 are connected,- respectively, by conductors t and 5, to the terminals of a source 6 of'direct-cnrrent energy. The electrode Z'coinprise's a pile 7 ot' carbon granules, which. may be contained in a receptacle f3, while the remaining eleot-rode which is movable relatively thereto, may be composed of copper.. A resistor 9 muv he connected in seriescircuit relation with the conductor 4 to maintain the current therethrough substantially constant. In practice, it has been found that the energy source may have an 'electroinotive force on the order of i2000 volts'and that thc resistance 'oi' the resistor 9 may be on theorder o a megohm. l

As previously stated, have discovered that, when the electrodes 1 and 2 are brought in Contact. and then slowly separated, an extremely fine line or chain llA of granules is formed therebetwec i Ithe resistance of which is extremely sensitive to sound waves.

When the current. traversing: the carbon chain 11 is held substantially constant by the resistor 9, the variations in the resistence thereof, which occur in the presence of sound waves, are translated. into potential variations having a wave-forni similar to that of the sound waves. 'The potential drop across the electrodes l and 2 is thus composed of a constant component, non' '.y,

currents ofcorresponding wave form by im-1 presslng the Y same through conductors 12 and 131 upon the grid and filament elements 14 and. 15, respectively, of a three-electrode vacuum tube 16, which includes, in addltion, a platev element 17.

'A condenser 18, having a negligible vimpedance to currents of sound-wave frequency, is included in the grid conductor .i515 12 and serves to prevent the so-calledq`uiet voltage drop across the discharge electrodes from operating to effect a blocking of the tube 16. A grid-leak resistor' 19 may be im,

eluded in a circuit 2 1 which, is connected in shunt relation to the grid 14 and to the lila- Inent element 15 in order to control the intensity of the negative charges which are accumulated on the grid 14.

A plateelament circuit-for the tube 1G includes a source 22 of direct-current energy and a high-impedance coupling resistor 23.

The oten'tial variations, which are established) across the coupling resistor 23^follow ing the variations in the resistance of the granular chain 11 in the presence of sound waves, may be impressed, through cond'uc tors 24 and 25, upon the input elements of a second' amplifying device -(not shown) or ciber circuit arrangement designed for em- 85 ploying such modulated'k electrical energy.

If a high-voltage source 'of energ 'iis emi ployed in place of the one shown in the drawing, say a generator having a voltage of several thousand volts, an electrostatic 4e Held may be established between the 'electrodcs l and 2 upon a breakage of the chain .11, which is sufiicient to cause the re-establishment of the chain. Thus, the chain ill may .be reformed upon an interruption thereof Without moving the electrodes 1 and 2, The advantage of such arrangement is obvious.

In .sunnnarizing the operation oflny iuvention, when a carbon-granule chain 11 is formed between theelectroftfs 1 and 2 and'` when the current therethrough is maintained substantially constant,- the effect of sound waves is to vary the resistance of the chain, thereby -causing potential variations across the electrodes 1 and 2 which correspond to the wave form of the disturbing sound waves. Thcpotential variations are then impressed upon the input electrodes 14 and 1f oi' the repeater device 1Gv aiid translated C" l`imo amplified potential variations across the ,coupling resistor 23 which is included in the plnh--ilamcnt circuit of the device 1G. Tlf.;-

amplified vor trairflatcd into variable cnr# if rents, as desired.

The extreme sensitiveness ofthe resistance of the chain of carbon granules m the presence of atmospheric-pressure variations resulting from .sound waves is believed to be due, in part, atleast, to the rclativel high contact resistanccs betweenthe granu es and to the large variations of such contact resistances in response Ato small variations 1nthe contact pressure. Under this-theory, the motion of the air due to sound Waves -tends to vary the length of the chain, making it alternately shorter and longer, and thereby altering the contact pressure between successive particles. i

lVhile I have described my invention as embodied in a particular circuit arrangement having specific values and while I have shown but one embodiment of lny'invention for the purpose of describing the saine and illustrating its principles of operation, itis apparent that various changes and modifications may be made without departing from the spirit ofmy invention. I"desire, therefore, that only such limitations shall be imposed thereon as are demanded by the prior art or indicated in the appended claims. i

'I claim as my invention:

1. A telephone system comprising an electrical circuitA including a source of energy, 05 sound-responsive means 'for introducing in said circuit a variable component substantially identical in wave form t` impressed sound waves, said means comprising a niass of carbon granules, an electrode spaced 100 tllereirmn and a chain of carbon granules said variable component for reproducing Ithe impressed sound waves.

3. In combination, a. pair of spaced electrorles, a chain of carbon granules therebetween and a source of energy operatively associated with said spaced electrodes, the magnitude .of the electric field between said electrodes being snicient to cause the reforming of said chain upon the breaking of? l y -thc same. luth-r potential. variationsv may be further 4. In' a telephone system, a circuitlinelud` ing a relatiyely large, substantially constantlcurrent resistance device, a relatively small 1430 variablefresistance device comprising a pair,

lish currents through said chain and t o`es.

tablish electrostatic forces across said pair of electrodes tending to reform said chain upon the chain being broken and energyamplifying means having its input terminals connected across said chain. f 6.An electrical device com arisingT a line chain of carbon granules hel( together by electrostatic forces only.

'7.'An electrical device comprising' a fine chain of granules of a substance havinLr af contact resistance sensitive to variations in thev contact pressure, and means for causing said granules to be maintained in chain formation by'electrostatic forces.

8. An electrical device comprising a fine chain of granules of .a substance having a contact resistance sensitive to variations in .the contact pressure, said chain being fr e from, mechanical support intermediate its ends, a source of potential, a circuit including said Source and said chain whereby the electrostatic forces between the ends of said chain will hold said chain together. and means for amplifying the variations in an electrical quantity in said circuit resulting from sound impinging upon said chain.

9. The method of detecting movements in a fluid non-conducting medium which consistsin maintaining, by electrostatic'attraction, a chain of granules of a substance having. a contact resistance sensitive to varia tions in the contact pressure and detectingv the changes in the chain resistance resulting from said Huid movements.

10.Y The .method of translating;r sound waves in a fluid medium which consists in maintaining, luy electrostatic attraction in said'inedimn, a chain of carbon granules and detecting the changes in the chain resistance resultiincr froni'said fluid movements.

11. In a sound-translating device, a chain of conductive particles exposed intermediate its ends to sound waves and means responsive to the changes of an electrical characteristic of said chain for delivering energy correspondingA to the sound,

12. The method of producing electrical response to sound, which consistsin estalilishingr, near the surface of a mass ol loose conducting particles, an electric field sufficient to form a chain of .said pa-iticleshniaine.

tainingacross said chain a difference of potential sulicient to keep the chain formed, and subjecting said chain to the sound.

13. In a sound translating device, a mass of loose conductiveparticles` an electrode outside said mass-a circuit including' said mass. said electrode, a source of electronic tive force and van impedance, the potential difference created by said source being Suliicient to cause av chain ot said particles to he established from saidmass'to said electrode and the magnitude of said in'ipedance beingY `greater than the changes of impedance caused by sound impinginpr on saidchain.

ln testimony whereof, I have hereunto subscribed my name this 25th day ot October i922.

JOSEPH SLEPAN. 

